The present invention is directed, in general, to semiconductor wafer processing and, more specifically, to an apparatus and method for reclamation and recycling of CMP (chemical/mechanical planarization) slurries.
In the manufacture of integrated circuits (ICs), chemical/mechanical polishing (CMP) is used to provide smooth topographies of semiconductor wafer substrates, on which the ICs are formed, for subsequent lithography and material deposition. These CMP processes are well known within the IC fabrication industry.
One major problem associated with this process involves post-CMP handling of the polishing slurry. It is well known that a large percentage, perhaps as much as 75 percent to 85 percent, of the slurry is never fully utilized during semiconductor wafer planarization. Because of the physical constraints of the polishing apparatus, the slurry that actually performs the planarization, i.e., xe2x80x9cusedxe2x80x9d slurry, is commingled with the slurry that is excess to the process needs, i.e., xe2x80x9cunusedxe2x80x9d slurry. Therefore, while not directly separable from the xe2x80x9cusedxe2x80x9d slurry, the xe2x80x9cunusedxe2x80x9d slurry is carried off into the waste slurry drain. As such, the xe2x80x9cwaste slurry,xe2x80x9d as it is considered, still comprises a large percentage of useable chemicals and abrasive.
A complicating factor for the process is that the polishing platen is frequently washed with de-ionized (DI) water delivered under pressure to the platen to rinse the platen of slurry between polishing steps. Of course, the DI water mixes with the waste slurry and dilutes the chemical etchants, thereby complicating waste slurry recovery and reuse. Presently, waste slurry, including the waste DI water, is collected from the polishing environment and given minimal processing so as to accommodate environmental concerns. That is, the slurry is processed to separate a majority of the solid particulate material from the liquid and the two by-products, the solids and liquids, are then disposed of by conventional methods. Therefore, considerable waste of the slurry component materials occurs. Also, a large portion of the liquid contains chemicals and increases the liquid volume that must be treated by the municipal water facilities. This larger-than-desired volume of liquid results in a higher-than-necessary bill for services from the municipal water treatment facility. Additionally, the greater usage of chemicals also contributes to increased cost.
Accordingly, what is needed in the art is an apparatus and method of use that efficiently separates waste slurry, including liquids, for recycling or reuse while minimizing liquid volume committed to waste water treatment.
To address the above-discussed deficiencies of the prior art, the present invention provides a polishing slurry reclamation system. In one embodiment, the polishing slurry reclamation system comprises a polishing apparatus having a polishing platen and a fluid delivery system positioned to deliver a slurry or a rinse to the polishing platen, a recovery drain adjacent the polishing platen, and a fluid diverter associated with the platen and configured to deflect a selected one of either a slurry or a rinse emanating from the polishing platen to the recovery drain.
Thus, in a general sense, the present invention provides a system and method for selectively diverting slurry or rinse water, whichever is currently in use, as it pours over the edge of the polishing platen to a selected recovery drain. Therefore, the user may minimize the volume of slurry and rinse water going into the sanitary sewer. This reduces cost by reducing the volume of waste fluids that is the basis of municipal charges for waste water treatment. The system additionally allows ready recovery of a highly concentrated waste slurry that may be either returned to the manufacturer for recycling or modified for reuse in the polishing process.
In another embodiment, the recovery drain is a slurry drain or a rinse drain. In alternative embodiments, the fluid diverter or polishing platen is selectively positionable to cause the selected one of either the slurry or rinse to be diverted to the recovery drain. In yet another embodiment, the fluid diverter comprises an annular diverter that is concentric about the polishing platen and configured to divert the selected slurry or rinse to the recovery drain when the annular boot is inflated. In a further aspect of this embodiment, the annular diverter may be an inflatable boot or a mechanical diverter.
In another embodiment, the fluid diverter is a fluid shield concentrically and selectively positionable about the polishing platen to divert the selected one of either a slurry or rinse to the recovery drain. In a further aspect of this embodiment, the fluid shield is in a fixed position adjacent the polishing platen.
The fluid diverter, in another embodiment, comprises inert gas nozzles positioned proximate a perimeter of the polishing platen and oriented to route the selected one of either the slurry or rinse to the recovery drain. In a further aspect of this embodiment, the gas nozzles are coupled to a gas nozzle conduit system integrally formed in the polishing platen. In a second aspect of this embodiment, the gas nozzles are adjacent the polishing platen and the system further includes a conduit system external the polishing platen and coupled to the gas nozzles. The conduit system is configured to deliver a gas to the gas nozzles. The gas discharge nozzles, in a third aspect of this embodiment, are connected to an inert gas source.
In another embodiment of the present invention, the fluid diverter is a vacuum system located adjacent the polishing platen and configured to remove slurry from the polishing platen. The vacuum system, in yet another embodiment, further comprises a vacuum system coupled to the recovery drain. The system, in another embodiment, further comprises a filter coupled to the recovery drain.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.